For reasons relating to measuring technology and for reasons of safety the potential of the electrical supply line of a radar sensor should be separate from the potential of the filling level container, which is often made of metal. This can for example lead to a reduction in the noise effects in measuring, and to a reduction in the susceptibility to interference of the measuring signals. Furthermore, such insulation leads to improved safety, for example in relation to the avoidance of fires that can occur as a result of a short circuit or a defect in the electrical supply or in the electronics of the filling level radar. Undesired spark-over could, for example, lead to ignition or damage of the contents.
WO 2005/038414 relates to a method and a device to insulate a filling level radar. In this arrangement the electrical insulator is arranged so as to be transverse in relation to an open end of a waveguide. The other end of the waveguide feeds the aerial. In this arrangement the insulator extends continuously over the entire cross section of the waveguide.